Radiation exposure is detrimental to human health. For example, a comprehensive review of available biologic and biophysical data supports a “no-threshold” risk model for radiation exposure since the risk of cancer may increase linearly at low doses of radiation without a threshold. The dose of radiation has the potential to cause a small increased risk of malignancy in humans. (National Research Council. Health Risks from Exposure to Low Levels of Ionizing Radiation: BEIR VIIPhase 2. Washington, D.C.: National Academies, 2006.)
For example, within the survivors of the Hiroshima and Nagasaki atomic bombings, which represents a large population that includes all ages and both sexes, more than 60% of exposed survivors received a dose of radiation of less than 100 mSv (the definition of low dose used by the BEIR VII report). (National Research Council, 2006.) The Radiation Effects Research Foundation (RERF) in Japan has conducted follow-up studies on these survivors for more than 50 years to evaluate the health effects of ionizing radiation. From these studies, it was found that the occurrence of solid cancers increases in proportion to radiation dose. (Preston D L, Ron E, Tokuoka S, et al. Solid cancer incidence in atomic bomb survivors: 1958-1998. Radiat Res, 2007; 168: 1-64., Cullings H M, Fujita S, Funamoto S, et al. Dose estimation for atomic bomb survivor studies: Its evolution and present status. Radat Res, 2006; 166: 219-54.) See also, Sanchez R., Vano E, Fernandez J M, Gallejo J J. Staff radiation doses in real-time display inside the angiography room. Cardiovasc Intervent Radiol, 2010.
However, many different medical radiologic procedures or examinations, such as electrophysiological procedures, cardiac catheterization, angioplasty, cardiac stenting, cardiac valve procedures, and orthopedic procedures require the use of radiation. Although many different technologies attempt to avoid or minimize radiation during these procedures, there is still a moderate to high x-ray exposure as evidenced by reported fluoroscopy in numerous studies. (Cano O, Alonso P, Osca J, et al. Initial experience with a new image integration module designed for reducing radiation exposure during electrophysiological ablation procedures. J Cardiovasc Electrophysial, 2015; 26: 662-670, Valderrabano M, Greenberg S, Razavi H, et al. 3D cardiovascular navigation system: accuracy and reduction in radiation exposure in left ventricular lead implant. J Cardiovasc Electrophysiol, 2014; 25: 87-93.) Implant procedures may incur a higher exposure to the practitioner since the x-ray generator may be closer to the practitioner.
Some technology allows real-time assessment of radiation dose exposure at a given location. In radiation protection dosimetry, two types of dosimeters may be used: passive and active (direct reading). Passive dosimeters, such as film badges, may integrate the radiation dose over the measurement period. Active electronic dosimeters may combine a detector with the readout to display the radiation dose value (e.g., the rate of radiation exposure). (Ankerhold U, Hupe O, Ambrosi P. Deficiencies of active electronic radiation protection dosimeters in pulsed fields. Oxford University Press, 2009; 135:149-153.) Real-time radiation dose feedback utilizing dosimeters have been shown to reduce radiation exposure to the practitioners. (Racadio J, Nachabe R, Carelson B, et al. Effect of real-time radiation dose feedback on pediatric interventional radiology stop radiation exposure. Journal of Vascular and Interventional Radiology, 2013; 25:119-126.)
During a radiologic procedure, a radiation source, such as an x-ray tube below the table holding the patient, may emit radiation (e.g., x-rays) as a direct radiation beam toward an area of the patient's body that is intended to be examined. Most of the direct radiation beam enters into the patient in order to allow the patient to be examined and subsequently exits the patient's body. The area of the patient's body that is under examination receives some radiation due to the direct radiation beam. The entrance radiation dose is the amount of radiation that enters into the patient and the exit radiation dose is the amount of radiation that exits from the patient.
However, radiation from the direct radiation beam deflects, which causes the radiation to scatter and forms “scatter radiation.” Scatter radiation refers to any radiation that is outside of the direct radiation beam. A portion of the radiation may scatter before and/or after the radiation enters into and exits from the patient's body. Some of the scatter radiation enters into areas of the patient's body that are not under examination. Accordingly, these areas of the patient's body not under examination also are exposed to and receive radiation due to the scatter radiation, which needlessly increases the patient's overall exposure to radiation (i.e., the exit radiation dose) and also increases the amount radiation exiting the patient (i.e., the exit radiation dose), which affects the practitioners.
The practitioners are also exposed to the scatter radiation, both the scatter radiation that has not entered the patient's body and the scatter radiation that has entered and exited the patient's body. The scatter radiation from areas of the patient's body that are not under examination, in particular, needlessly increases the amount of radiation that the practitioners are exposed to.
In order to reduce the amount of radiation that the practitioners are exposed to (specifically due to the radiation exiting the patient), lead skirts that are attached to the side of the x-ray table, mobile seals, suspended plexiglass shields, and sterile pads placed on top of or above the patient may be used. Most of these devices are on the top of the examining table and are only designed to shield the practitioners from the radiation exiting the patient. These devices do not protect the patient from excessive radiation (e.g., scatter radiation) entering into areas of the patient's body not under examination and instead allow the patient to be needlessly exposed to the scatter radiation. Furthermore, the shielding above the patient on top of the examining table may lack symmetry in placement, which may create gaps in protection to the practitioners. Even further, it may be difficult to move shielding that is positioned on top of the procedure table in order to visualize different portions of the patient's body.
Therefore, certain procedures, such as cardiac catheterization, expose areas of the patient's body that do not need to be visualized to radiation, which may needlessly increase both the patient's and the practitioner's overall radiation exposure.